OK I have both. I have had 2 Century C93s, and finally own one C93 and on genuine HK93.
I will say this. The C93s I have had were reliable and functioned well enough. BUT...side by side, there is a big difference.
Not only in the quality of the build, but in the way they function. For example the Century made receiver magwells on my 2 C93s were way too tight. Actually made mag changes slower. And things like the cocking handle were not well done on my C93s. They were sticky and required some force to start the cocking pull. The cocking handle on the genuine HK is smooth as butter. Everything better put together.
The US made pistol grip assembly on the C93s has a lot of flashing, and generally feels cheap. Genuine HK93 pistol grip assemble is smooth and feels very solid, ergos are way better. Same with the selector switch, etc.
The C93 is also slightly different since it is made from an HK33 parts kits, and while the parts are interchangeable, it has a carry handle where the HK93 doesn't for example.
I pretty much just keep the C93 around for spare parts. If I am going to shoot, I will shot the HK93.
Honestly, the C93 will cost you ~ $600-700. I picked up my HK93 with a surefire tac light and bayonet mount for $2200.
While it seems like a lot, I am glad I did, once I saw the differences. Mags are expensive, but I bought several of the HK steel 30 round mags, they are more useful than the 40 round aluminum, though the 40s look cool.
As for the $1500 clones, I don't see the point. If you look you can find the real deal for not much more. Unless you just want a 1/7 barrel and picatinny rail in an HK93 format, it doesn't really make sense.
Hope that helps.